Experimental and theoretical studies on gold(iii) carbonyl complexes: reductive C,H- and C,C bond formation

The reactivity of cationic (C<^>C)gold(iii) carbonyl complexes was investigated. While the in situ-formed IPrAu(bph)CO+ complex (bph = biphenyl-2,2 '-diyl) does not undergo a migratory insertion of CO into the neighboring gold-carbon bond, nucleophiles can attack the coordinated CO moiety intermolecularly. Water as a nucleophile initiates a CO2 extrusion combined with a reductive C,H bond formation. The rapid formation of a gold(i) species from an intermediary gold(iii) carbonyl has not been observed before and shows a significant difference in reactivity between (C<^>C) and (C<^>N<^>C)gold(iii) carbonyls. The latter have been reported to form stable gold(iii) hydrides via the WGS reaction. In the case of methanol acting as a nucleophile attacking the gold(iii) carbonyl, no extrusion of CO2 is observed. Instead an intermediary gold(iii) carboxyl complex forms an aryl carboxylate via reductive C-C bond elimination. Experimental and theoretical studies on the mechanism explain the observed selectivities and give new insights into the reactivity of elusive gold(iii) carbonyls.